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Many people think that everything leads to cancer, and therefore it’s useless to try to prevent it. New research shows that although this attitude is common, it doesn't reflect the truth about cancer prevalence and prevention. Tune in to learn the facts.

We’re joined by Dr. Michael Thun who heads epidemiological research for the American Cancer Society.

As always, our expert guests answer questions from the audience.

Announcer:

The opinions expressed on this webcast are solely the views of our guests. They are not necessarily the views of HealthTalk, our sponsors or any outside organization. And, as always, please consult your own physician for the medical advice most appropriate for you.

Judy Foreman:

Hello and welcome to Health Talk Live [HealthTalk Live has been renamed Health Now with Judy Foreman]. I'm your host, Judy Foreman.

Many people think that everything leads to cancer and therefore that it's useless to try to prevent it. But new research shows that although this attitude is very common, it doesn't actually reflect the truth about cancer prevalence and prevention. Tonight you'll get the facts on cancer and its causes.

I'm very pleased to welcome tonight Dr. Michael Thun. He heads epidemiological research for the American Cancer Society. Dr. Michael Thun, thank you so much for joining us tonight.

Dr. Michael Thun:

I'm pleased to be here.

Judy:

Good. So our goal tonight is not to try to understand cancer at a molecular level, fascinating as that is for some people, but to look at people's attitude towards cancer and how those attitudes affect behavior. So Dr. Thun, tell us briefly about this new study that was published recently in the Journal of Cancer Epidemiology Biomarkers and Prevention. One of the things in the study was that almost half of the 6,000 plus Americans who were interviewed, felt that almost everything causes cancer. In reality, what do we know that does cause cancer?

Dr. Thun:

Well, first of all fatalism it is a bigger problem than one might think, and the concern is that feeling hopeless may lead to people not to do the things that could save them years of healthy living. There's a rather short list of things that have a large effect on your individual risk of developing cancer and also your overall health risks. And the most important in terms of reducing the risk of both getting cancer and dying from cancer are on top of the lists is to avoid all forms of tobacco. The second would be to maintain a healthy body weight. The third is to adopt a physically active lifestyle. Then, eat a healthy diet with an emphasis on plant sources. If you drink alcoholic beverages, limit consumption. And get the recommended screening tests – those are all coming from the American Cancer Society guidelines.

Judy:

And which are the recommended screening tests?

Dr. Thun:

They begin at different ages for different cancers. For breast cancer the American Cancer Society recommends mammography beginning at age 40. There are screens for colorectal cancer beginning at age 50 in average risk people, and there's regular screening with PAP tests for cervical cancer. Then the recommendation with respect to PSA testing for prostate cancer is that men be informed about the pluses and minus of screening that we know at this point.

Decades, yeah. Although some people do get lung cancer without smoking. So tell us how strong that link is between smoking and lung cancer.

Dr. Thun:

Sure. So active cigarette smoking is overwhelmingly the most common cause of lung cancer. About 90 percent of cases in men and slightly over 70 percent of women.

It causes all types of lung cancers. The other causes involve second-hand smoke, other smoke products, other lung carcinogens like radon, asbestos, smoke from coal, certain metals and radiation therapy. So, the lung cancer in life-long nonsmokers affects somewhere between 17,000 and 26,000 people a year, which – if you considered it as a separate category - it would rank among the six to eight most common fatal cancers. Sort of, about as common as lymphomas if you group them or leukemias.

Judy:

That is, lung cancers in people who were never smokers?

Dr. Thun:

Yes.

Judy:

Particularly with women you said, you know, there's a 70 percent of cases of lung cancers in woman are caused by smoking. But what's causing the other 30 percent then?

Dr. Thun:

Right. Well first of all, the percentage of lung cancers that are caused by smoking in women is rising because the women who are long-term smokers are now well into the age where lung cancer risk from very long term smoking is high, so the percentage is likely to rise to be similar to that in men. But the most likely things on that list that I gave you would be second-hand smoke and radon. Those being the most widespread exposures among woman.

Judy:

Okay, and where are we getting the radon from? Where is that exposure actually physically coming from?

Dr. Thun:

Well that is a natural decay product of uranium. That comes as a gas that seeps through cracks in the walls of cellars in areas of the country where there are radon cells. Once it gets measured, you can have ventilation put in to reduce it. So, when it's not a smoker, most of the lung cancers are caused by radon or are caused by the joint effects of smoking and radon.

Judy:

Oh, I see. Okay.

Dr. Thun:

It's a correctable problem and there, the E.P.A. can provide advice about how you get tested and how you correct it.

Judy:

Okay. How about breast cancer? To my knowledge, what we know about the causality of breast cancer is that two inherited genes. BRCA1 and BRCA2, do quite clearly raise the risk of breast cancer but what else does? Is it not having babies? Having too few babies? Or having them too late in life? Is it being overweight? Is it not exercising enough? Is it hormone therapy? Is it birth control pills? Run through for us what do we know about the causality of breast cancer because it is something on the minds of many many woman.

Dr. Thun:

Sure. You can divide the factors that increase risks into those that are modifiable and those that are generally not modifiable. So among the modifiable ones: being overweight or obese after menopause, physical inactivity, use of postmenopausal hormone therapy especially estrogen and progesterone combined therapy, alcohol consumption, not breast feeding and there's a small increased risk during the use of birth control pills.

Now, among the ones that you can't modify, the biggest is age, and then there is a family history and inherited genes. You mention BRCA1 and BRCA2, which account for about only 5 percent of breast cancer. About two weeks ago, there were several reports identifying six other genes that were associated with small increases in risk. Then, there are lifestyle factors or other biological factors that are long periods of having menstrual periods (menstruation starting at an early age and ending late), later age of first birth, fewer babies – basically the reproductive patterns that are typical for developed countries.

Judy:

So, as I understand it, it's the number of menstrual cycles that a woman has, the bigger that number, the higher the risk. Is that because every time you ovulate, you get a blast of estrogen and other hormones that can drive insipient breast cancer?

Dr. Thun:

Exactly it. The estrogen blast is causing breast tissue to proliferate like crazy and then to regress, and every time that happens, it increases the chances of genetic glitches getting copied and being divided into more cells.

Judy:

Let's talk for a second about pregnancy and breast feeding. I thought that the more pregnancies a woman had and the earlier in her life that she had them, the more protected she was against breast cancer, and that breast feeding was kind of a separate factor.

Dr. Thun:

You're exactly right. The breast tissue is one of the few tissues in the body where the cells don't completely differentiate. They don't become fully adult until the first pregnancy. And so the earlier that the first pregnancy occurs, that sort of sets breast cancer risk at a lower level throughout the rest of life, even as it continues to increase with age.

Judy:

So why does breast feeding protect against breast cancer?

Dr. Thun:

I'm not totally sure of the physiology, but I know that it is an established protective factor, and some if it's because of the hormonal effect. One of the interesting things about breast cancer is that we know a lot more about the things that affect the later stages of breast cancer development than we know about things that affect the kind of initial genetic glitch. So what all of these factors related to hormones do is they basically increase the likelihood that any kind of a mutation or genetic problem will get proliferated into enough cells so that they actually leads to invasive breast cancer. We know a lot less about the early stages.

Judy:

So that's kind of the difference. These things are what you would call promoters and the actual first causes or the initiators, and we don't know that much about the initiators. Is that what you are saying?

Dr. Thun:

We know less. It's part of the study.

Judy:

A lot of women, particularly breast cancer activists, insist that there are a lot of "environmental" causes of breast cancer. To my knowledge, there's no evidence that anything in the environment causes breast cancer, but am I wrong?

Dr. Thun:

First of all, cancer researchers consider anything environmental that is outside of the genes that you inherit at the time of conception. So they would consider all of the things we have just been discussing as also environmental.

Judy:

Yeah, it's such a shame because it really is a confusing debate because you'd be considering alcohol and birth control pills and hormone therapy and all that is environmental. But I think what lay people mean is pesticides.

Dr. Thun:

Exactly. So definitely that's a confusing issue. But another distinction that's important is the factors we've been talking about, the ones that we know have a substantial effect on the individual woman's risk of developing breast cancer. And except for high dose radiations such that you get with therapy or extreme, there are no environmental cautions that have been established, proven to have a substantial effect on an individual woman's risk of breast cancer. This is does not mean at all that we know everything. There is still a lot to learn about exposures that may affect critical periods of life. And those issues are difficult to study with the tools we currently have available, but it may well be that there are important things we don't know about factors that affect breast cancer risks.

Judy:

Well, for instance, hasn't there been a big, long-lasting, so called, cluster of breast cancer cases on Long Island? And haven't people studied that quite a bit but not found any, of the kind of environmental links that lay people think of as environmental?

Dr. Thun:

That's the case however the advocacy groups in Long Island would argue, that studies that were done have looked at exposures in adulthood and that they didn't look at exposures in early life, in utero. But I think that the underlying dilemma is that the ways that we deduced breast cancer risks are all difficult, and there may well be other factors out there. Breast cancer is such an intensely emotional topic that it brings a lot of heat to the debate about causes.

Judy:

It does, which is probably the moment to remind everybody that although most women are most afraid of breast cancer, six or seven times as many woman actually die of heart disease, which nobody worries about, although they should. But that's just a little plug for heart disease.

Dr. Thun:

Also, more woman die of lung cancer than breast cancer.

Judy:

And lung cancer – what about colon cancer? What do we know in terms of the causes of colon cancer besides increasing age?

Dr. Thun:

If you group cancers of the colon and rectum together, it's number three in terms of death in both men and woman, and the known avoidable risk factors are being overweight and obese. That's a stronger relationship in men than in woman, being physically inactive, having a diet that's high in red or processed meat, smoking is likely to be a risk factor, although it's not 100 percent established, and high alcohol consumption is likely to be a risk factor although it's closely linked with smoking.

Judy:

What about chronic Inflammatory Bowel Disease? Does that raise the risk?

Dr. Thun:

Definitely. Ulcerative colitis and to a lesser extent Crohn's Disease increase the risk because the chronic inflammation is almost like having a wound that doesn't heal, and the cells keep replicating trying to heal it. That increases the likelihood that genetic glitches will develop into cancers.

Judy:

Right. Just sort of a quick translation, the more often a cell divides, the more chance there is for these mutations to happen with every cell division, and that can lead to cancer. But I don't quite get why being obese and physically out of shape would lead to colon cancer. I mean, what's the connection? The fat jumps from your stomach to somehow inside your guts and causes cancer? What can be going on?

Dr. Thun:

It doesn't do any jumping. We used to think of fat as being inert, essentially like macadamia nuts just sitting there. But fat is highly active as an endocrine organ, particularly fat that is inside the abdominal cavity, the kind that men get with abdominal obesity. That leads to a strong risk factor for developing insulin resistance and developing type 2 diabetes. Along with the high insulin that is produced in that state are high insulin-like growth factors. So one presumes the mechanism is through insulin resistance and insulin-like growth factors, and that would be consistent if it were the mechanism with men having a stronger relationship to obesity than women.

Judy:

So basically the fat that we all love to hate in our stomachs and the deep visceral fat is actually a factory for these inflammatory factors called cytokines. They kind of get you going on this path towards metabolic syndrome, which is an increased risk of cancer plus heart disease and diabetes and lots of other bad things. Is that basically right?

Dr. Thun:

That's it. It produces the inflammatory factors, and it also produces the insulin-like growth factors, and it reduces the liver's ability to make the carrier protein, so there is more of those pre-growth factors floating around.

Judy:

And growth factors basically stimulate cell division and back again the cell dividing more often and that raises the risk of mutations that can lead to cancer.

Dr. Thun:

Exactly.

Judy:

So it all does make sense. What about alcohol consumption? How does that fit in with colon cancer? You would think that doesn't necessarily make you fat. Why would alcohol raise the risk?

Dr. Thun:

Alcohol consumption is not as firmly established of a risk factor for colon-rectum cancer as obesity and some of these other factors. The other thing is that high alcohol consumption is closely associated with smoking, and so there's been sort of a lot of work to try and disentangle the effect of long-term smoking from an effect of heavy drinking.

Judy:

So if inflammatory factors and the insulin-like growth factor raise the risk of colon cancer, do anti-inflammatory drugs called NSAIDS, like ibuprofen, do they lower the risk? Had that been shown?

Dr. Thun:

That's definitely been shown. Actually that's a very interesting, long story. The first human evidence of it was related to aspirins and the reduced risk of colon cancer. Then all during the '90's many studies replicated that, and they found a reduced risk also with other anti-inflammatory drugs. What has prevented using that for cancer prevention is that the risk of bleeding from these drugs offsets the benefits in terms of cancer reduction for an average risk person. So unless it can be shown that the prolonged use of aspirin reduces the risk of all cancers, you can't show that the risk-benefit ratio is favorable. So that's the next hurdle.

Judy:

Okay. I've heard that hormone replacement therapy in women can reduce the risk of colon cancer. Is that true?

Dr. Thun:

Yes it is.

Judy:

Why would that be?

Dr. Thun:

Well, there are estrogen receptors and progesterone receptors on the cells that line the colon. Their function isn't entirely clear, but even in the Women's Health Initiative, which was an experimental study in humans, the risk of colon cancer was decreased in the women who were given the hormone replacement treatment.

Judy:

But we don't really know why.

Dr. Thun:

We don't exactly understand what those estrogen receptors are doing in the colon itself.

Judy:

Well, they are pretty much everywhere throughout the body, aren't they?

Dr. Thun:

That's right. We understand what they're doing a lot better in breast tissue and in endometrial tissue [that lines the uterus] and in the ovaries than we do in things like colon and lung, etc., where they are also found.

Judy:

And brain.

Dr. Thun:

Yes.

Judy:

But we are not going to go through every cancer. We couldn't do that unless we had more hours than we've got. And we certainly do hope that listeners will call in with specific cancer questions, but I definitely did want to touch on prostate cancer. What do we know about the causes of that at this point?

Dr. Thun:

Well, we know remarkably little. We know that the risk goes up with age, and that it's highest in African-American men.

Judy:

That was my next question. Why is it higher in African American men?

Dr. Thun:

Well, that's an open question. There may be a different answer depending on whether you are talking about being diagnosed with prostate cancer versus dying from prostate cancer because with respect to dying, African-American men may have less resources to get appropriate treatment. It has been known for a long time that prostate cancer rates are also high among African descendants in the Caribbean and so whether or not there is an inherited factor that contributes to prostate cancer, risks in African American men is still an interesting area of research, and actually there is a study going on now to look at the parts of Africa from which many slaves descended.

Judy:

I was going to ask you about Africa and if they have more prostate cancer. But, of course, prostate cancer tends to strike later in life, and if you've already died from AIDS or malaria by age 40, we'd never know about the prostate cancer.

Dr. Thun:

That's right. And then the detection systems and the medical systems to diagnose this aren't really going to pick up a large percentage unless you have a special registry where you do that intensively.

Judy:

So we don't really know what causes prostate cancer. I mean, there is a family history connection, but aside from that, we don't have anything analogous to the BRCA1 and 2 genes. Right?

Dr. Thun:

Well, actually we now have the first genes that are associated with prostate cancer, which was picked up in a study in Iceland. It found an area of the genome, which is relatively thought to not have genes in it. And that association was replicated now in three or four large consortia [study groups], and there are a number of different mutations in that area [of the genome] which came independently associated with risks. But we still don't really have a clue what that part of the genome does. And so there is an intensive hunt to find exactly how this is happening.

Judy:

And we're still not recommending that all men of a certain age get the PSA or Prostate Specific Antigen test because it's so confusing, and it leads to a lot of intervention that may not be necessary. Is that right?

Dr. Thun:

Well, the real reason why it is recommended that men get counseled about the pluses and minuses rather than recommending the test is that there hasn't been evidence from randomized clinical trials or big experimental studies showing that early detection actually improves survival, or saves lives. That trial is ongoing, but there has been a remarkable decrease in the death rate from prostate cancer since 1991. It's about a 35 percent decrease.

Judy:

And to what do we attribute that?

Dr. Thun:

Well, as with breast cancer, there have been both early detection and improvements in treatment. For breast cancer, the analysts have suggested that the credit is about equally divided. For prostate cancer, we don't know, but the decrease is real. It's not a function of finding cancers early because it's the decrease in the actual rate per 100,000 of men dying from prostate cancer.

Judy:

Okay. What about some of the blood cancers – lymphoma, leukemia? Are they on the rise? And if they are, does anybody know what the causes are?

Dr. Thun:

They are on the rise, and the causes have been in dispute. Some of the increase in non-Hodgkin's lymphoma was related to the AIDS epidemic because there are AIDS-related lymphomas that increase. And the occurrence of those has decreased with the advent of intensive treatment for AIDS. Just as the treatment got rid of the unusual kind of skin cancer called Kaposi's sarcoma, it also reduced the risk of these lymphomas. But the reason for the residual increase is unexplained, and so it's one of the cancers in which there are a number of environmental hypotheses. There are hypotheses having to do with vaccination and changing the age in which different things happen in the immune system. But basically at this point, we still don't know.

Well, the hypothesis is that aspects of the immune system mature at different stages in childhood.

Judy:

And by the way lymphoma and leukemia are essentially cancers of the immune system.

Dr. Thun:

Right. The lymphoma is of the lymph nodes and leukemia is of the white blood cells.

Judy:

B-cell lymphoma is also of the blood cells.

Dr. Thun:

Exactly. There's nothing really more confusing than the lymphomas. But the hypothesis has been that before vaccinations, we all got infectious diseases at an early age and with all of the results in death and illness, but with vaccinations, we have sort of changed the age in which the immune system is exposed to various infections. And so one of the hypotheses is, that may play a role. If it were true – and it's far from proven - it would be a bad consequence of a good thing because immunizations have hugely decreased infant-childhood mortality and had great benefits.

Judy:

Well, is it because fighting off these infections leads to more cells in your immune system becoming more mature and therefore less likely to turn cancerous? And without that kind of workout early in life, that doesn't happen?

Dr. Thun:

The general hypothesis would be the age in which the immune system is exposed to a particular infection may in rare cases result in a cancer.

Judy:

Okay. We're going to take a very short break now. Stay with us. This is Health Talk Live.

Judy:

You are listening to Health Talk Live. I'm Judy Foreman. Tonight out topic is cancer. Our guest is Dr. Michael Thun. He heads epidemiological research for the American Cancer Society.

We have some e-mails that have come in now. One is from Sue and she writes, "I've had rheumatoid arthritis for almost 30 years. I have now just been diagnosed with breast cancer. Is there any research which shows a link between having rheumatoid arthritis and an increased risk for breast cancer?"

Dr. Thun:

No, there's no link that I am aware of with breast cancer. Rheumatoid arthritis has been associated with increased risk of lymphomas and with a decrease risk of a colon cancer. The lymphoma is thought to be because of the chronic immunologic activity of the condition. The colon cancer was thought to be because of the anti-inflammatories used to treat the disease, but I am not aware of any connection to breast cancer.

Judy:

Actually that's a really good segue to our next e-mail which is from Colleen and she writes, "I have rheumatoid arthritis, and I take methotrexate and Enbrel to treat it. I understand that these medications can increase the risk of lymphoma. Should I be nervous about getting cancer from these medications?"

Dr. Thun:

That's a difficult question because the medications are probably absolutely essential to her functioning and coping with her rheumatoid arthritis, and I don't know the absolute increase in risk. And it's impossible to recommend that someone not be nervous about something because that's mostly determined by your…

Judy:

…tendency to be nervous or not.

Dr. Thun:

Yeah, your tendency to be nervous. So I think that those medicines are powerful medicines, and I am sure that she has fairly frequent visits with her doctor, so they would be among the potential consequences although not common consequences to look for.

Judy:

Yeah. But, as you said, you don't really have a choice if you need those medications to function.

Dr. Thun:

Exactly.

Judy:

What about cancers of the mouth and throat. It's long been known that alcohol and smoking are risk factors for esophageal cancers, but what about the papillomavirus? Is that emerging as a cause for these kinds of cancers as well?

Dr. Thun:

Yes, it is. And the heavy alcohol consumption in conjunction with tobacco is just a huge risk factor for cancers of the mouth and throat and larynx. But what has been discovered in the last ten years is that the human papillomavirus is not only closely related to cancer of the cervix but it's also thought to be related to some fraction of cancers of the mouth and throat. And it's really part of the realization of how important infectious organisms are for different kinds of cancer, which went from knowing virtually nothing 20 years ago to realizing that infectious agents are central for cancers that are major in parts of the world – stomach cancer, cervical cancer, liver cancer and others.

Judy:

Yeah, we sort of think of infection and cancer as totally separate categories, but they are not. That's not really true. Just to go back to something you said - you said heavy alcohol and heavy smoking together are a big risk factor, but is the big culprit smoking? I mean how much does alcohol contribute to that? Or does alcohol alone lead to throat cancer?

Dr. Thun:

Smoking is more important than alcohol. First of all, heavy alcohol consumption is bad for a whole bunch of reasons. So, there's so many reasons to avoid smoking and to avoid heavy alcohol consumption. It wouldn't just be limited to this. But the two together increase risk of these cancers, 20, 40-plus fold.

Judy:

That's a huge increase.

Dr. Thun:

Yes.

Judy:

In terms of the papillomavirus and these throat cancers, if there a strong enough connection, that that would make me wonder whether people should take the new HPV, the human papillomavirus vaccine, to protect against throat cancer.

Dr. Thun:

I don't know how much the recommendations have been worked out with respect to cancers other than cervix. So I can't answer that question.

Judy:

Okay. Fair enough. Yes, it's a very new vaccine, so it's not surprising that all the answers aren't in yet. We got this e-mail from Pam, who writes, "I was not able to listen to your show last week on coffee." And by the way it was a fascinating show. We found out lots of good news basically about coffee. And she wants to know, "do researchers think coffee can cause cancer?" Dr. Thun what do you think?

Dr. Thun:

Well, the answer is that they don't think it can cause cancer and the issue has been studied a lot partly because back in the early 1980's, that study came out of Harvard suggesting that coffee increased risks of pancreatic cancer and that result turned out to be due to methologic problem in the study.

Judy:

So it was just plain wrong?

Dr. Thun:

They got the wrong answer.

Judy:

Yeah.

Dr. Thun:

Yeah, it was because it was a hospital-based thing, and the control group they were in just got the wrong answer. But coffee is an extraordinarily complex mixture of chemicals, some of which might be expected to increase cancer risks, some of which might be expected to decrease cancer risks. But despite all of the studies that have been done, basically there is no evidence of increase cancer risks.

Judy:

Well, that's great. It's not too often in medicine that you get kind of a green light for something good like coffee. So, just to pause and recap here for a second, we started out saying that many people according to this newly published survey think that almost everything causes cancer, but from what you just told us, that's not really true. Is that correct?

Dr. Thun:

That's definitely not true. And as I said, the fatalism that comes from thinking everything causes cancer and there is nothing you can do about it and there's so many recommendations, it's hard to follow. That can cost people their lives if they don't do the things that we are really quite sure about.

Judy:

Yeah, and that brings me sort of to the next point, one of the other things in this recent attitude survey, was a finding that about one quarter of the respondents felt that there isn't that much they can do to lower their risk of cancer, but what can people do to lower their risk?

Dr. Thun:

Well, we went through the short list earlier.

Judy:

Yeah, exercise, diet, avoiding obesity

Dr. Thun:

Avoiding tobacco

Judy:

Avoiding tobacco

Dr. Thun:

If you drink alcohol, limit consumption, get the recommended screening tests, be physically active. One of the things about these additives that makes them a little difficult to interpret is that this becomes a rationalization for people who know in their hearts they should quit smoking, and it's too much work. Or they know that their weight is a big problem, and they don't know what to do about it. Some of this actually reflects not knowing how to actually move ahead on clear, obvious risk factors that could be modified.

Judy:

Well, we all know what's good for us and what's bad for us. But changing behavior, actually losing weight or stopping smoking, can be really tough. So we have another e-mail, this one is from Suzanne and she writes, "Do multiple sclerosis patients have more cancer than other groups of people?

Dr. Thun:

So that has been studied and the results are mixed. It's definitely not a condition on which there is solid evidence of any increased cancer risks. Though, I think it's still a little up in the air.

Judy:

So we don't really know?

Dr. Thun:

Right.

Judy:

And then we've got another e-mail from Jennifer. And she writes, "My father passed away from two cancers. He had lymphoma and then colon cancer. My mother survived breast cancer six years ago and bladder cancer one year ago. You can't imagine how difficult it is for me to get a high risk colonoscopy with Medicaid, especially being under 50. I'm only 44, but if my dad had only been brave enough to get a colonoscopy, he'd probably be alive today. Why can't people like me with two parents full of cancer get insurance to cover a colonoscopy?"

Judy:

Maybe you should divide that into two parts and talk about what the actual hereditary risk is and then the insurance question.

Dr. Thun:

Yes, so with respect to colon cancer – did I miss at what age her father developed colon cancer?

Judy:

She didn't say.

Dr. Thun:

So, a family history of colon cancer does increase risk – it doubles it. And there are different guidelines for screening in people who have higher risks, depending on the conditions. So that's something to talk about with her doctor.

Now, the issue about what is covered by insurance and what isn't is sort of a national problem, because the American Cancer Society has been campaigning and advocates strongly to have prevention and early detection covered by health insurance. And is it a state-by-state and company-by-company battle. Essentially the health care system needs to consider preventive care and early detection to be a central and essential part of standard medical care. And needs to cover that. And that's going to be a long battle.

Judy:

Wouldn't it be cheaper for insurance companies to pay for the screening – especially with colonoscopy which can basically catch cancer so early that you would never go on to get it - wouldn't be cheaper to let everybody who wanted to have a colonoscopy, have one and avoid some colon cancers down the line?

Dr. Thun:

Though it is definitely cheaper to society, insurance companies factor in what the likelihood is that someone's going to change to a different insurance company. So, with something like smoking cessation or colonoscopy, one company may be paying for the test and another company may be reaping the benefits. So really what is needed is an approach that it guarantees it, so that it's not this "winners and loser" mentality.

Judy:

Yeah, having the insurance companies fighting to not cover people is not really to the public good. There was some news this week about ovarian cancer, and some of it came from you, the American Cancer Society. I gather that you and some other groups released a list of ovarian cancer symptoms. It's a little bit controversial because the symptoms are not very specific but the message seems to be that women who have these symptoms should check with their doctors. Tell us why you and the other groups decided to come out with this kind of checklist of ovarian cancer symptoms and what you found or what you said.

Dr. Thun:

Ovarian cancer continues to be a very lethal cancer because it's usually diagnosed after it has spread, and it's therefore much harder to treat. What we really need is sensitive and specific blood tests that would be an early indicator of ovarian cancer. There's been efforts to develop that, but we don't have that yet. So this latest effort is an approach that's less precise but which is to recommend that woman who have a prolonged sense of bloating and filling up when after, during eating etc, go and get that checked with their doctor. It's sort of an attempt to do something useful while waiting for the development of a really good predictor test.

Judy:

So we know that if you get ovarian cancer, and at the time of diagnoses you're at one of the later stages, that things are not terrifically helpful, but is there actually evidence that catching it early will save lives? Do we catch it early so seldom that we don't know the answer to that?

Dr. Thun:

I think that's it. It's like pancreatic cancer. I mean we know that when ovarian cancer is diagnosed and it's localized, it has a far better survival rate than when it's already metastasized, than when it's spread. But what we don't have is a screening approach in which we can tally up the effects on improving survival.

Judy:

Yeah. That's just been so illusive. It's very frustrating. Go back again to the attitude survey that we have been talking about all evening. One of the other things that showed up in that survey was that almost three quarters of the respondents felt that there were so many recommendations about preventing cancer just kind of floating around on the air waves, that people don't really know how to assess what recommendations are true and what are not. So can we go back to your recommendations and go kind of piece by piece? Clearly people shouldn't smoke. That's just not even controversial. Right?

Dr. Thun:

Yes.

Judy:

And just how long, when you quit smoking, how long does your risk of cancer stay elevated, and when does it go back down to normal?

Dr. Thun:

Well, what actually happens is that when we age, the risk of most cancers goes up. So if you are continuing to smoke, that increase with age is very steep. If you never smoke, you have an increase with age but it's much less. When you quit smoking, your risk depending on the age at which you quit moves over towards the projectory as if you never smoked. So the appropriate comparison is, if you're a smoker, it's really irrelevant to whether or not your risk remains a little bit higher than if you've never smoked. The real gain is how much risk you're avoiding by not continuing to smoke.

Judy:

So, it always pays to quit. There's not ever a point where you might as well keep smoking?

Dr. Thun:

That's right. I mean if you're dying from cancer and at the end stage, then it's not going to affect…

Judy:

…change things.

Dr. Thun:

But quitting is extraordinarily beneficial at any age.

Judy:

Okay, and tell us about exercise. I mean, that's certainly something that people can do but have trouble doing. How strong is the evidence that exercise can lower the risks of cancers, and which cancers in particular?

Dr. Thun:

The two cancers that there is the most information on are colorectal and breast cancer. And there are a lot of studies, non-experimental studies that very consistently showed lower risk of colorectal cancer in people who exercise even moderately. For breast cancer there are lots of studies that show with more vigorous physical activity, there is lower risk. The thing that makes it even more persuasive than being causal is that with exercise several of the intermediate factors that are thought to worsen the risk of colorectal cancer get better. So for example, it's very clear that physical activity improves insulin sensitivity. It gets rid of the bad effects of being overweight and sedentary. And that happens rather quickly, so this evidence of short-term benefits from exercise is even more extensive for diabetes and for heart disease and conditions like that, but it has been designated as conclusive for cancers.

Judy:

So that's both breast cancer and colorectal in particular have been shown to benefit from exercise?

Dr. Thun:

Right.

Judy:

Isn't it also true that women who already have breast cancer especially postmenopausal women who exercise a lot have a lower risk of recurrence?

Dr. Thun:

Right. There's less literature on the effects on prognosis and recurrence and so on, but for both weight-control and for physical activity, there's accumulating evidence that it should be an important component of treatment.

Judy:

Okay, and what about alcohol? You kind of sprinkled that throughout the conversation. We've all read that alcohol can increase the risk of breast cancer, but that increased risk is relatively minor, isn't it? And isn't that increase offset if the woman also takes folic acid?

Dr. Thun:

So, the second part of your question about the folic acid is suggested by several studies, but it has never really been accepted as conclusive, nor has it been dismissed. And folic acid deficiency has become less common since late 1990's when grains were fortified with folic acids. So, as far as the magnitude of the increase of risk, it is the related to how much you drink. It begins going up at even one drink a day, but it keeps going up the more a woman drinks, and it goes up to something like 1 in 5 with substantial alcohol consumption. So it's there and it's not to be minimized, but it's complicated by the fact that moderate alcohol consumption is associated in middle-age people with lower risk of heart disease.

Judy:

Right, which is more likely to kill you.

Dr. Thun:

In middle age, actually breast cancer is more common. There's an age period in mid life in which breast cancer risk is bigger than heart disease risk for a woman, so it's a complex equation. I think the rule of thumb is that if you are a woman, moderate consumption consists of less than or equal to one drink a day. And if you are a man, it's two drinks a day. And beyond that, the detrimental effects accumulate and essential heart benefits do not.

Judy:

And what about diet? Especially fruits and veggies that you, the American Cancer Society, have been hammering at us for years to eat more fruits and veggies. What is the actual evidence on the cancer prevention effects of these dietary things?

Dr. Thun:

Right. So the evidence that fruits and vegetables reduce cancer risks is weaker than what was originally thought, although it's still strong for heart disease. The International Agency for Research on Cancer, a part of the World Health Organization, has concluded very low intake of fruits and vegetables can increase cancer risks particularly in cancers of the esophagus and stomach. And that's important worldwide, but less important in the United States. The other issue is that a diet that's high in fresh fruits and vegetables affects satiety, how satisfied you feel in terms of what you're eating and displaces food with higher caloric density, and so the rule of fruits and vegetables consumption in weight control is important and all of the major health organizations still recommend diets high in vegetables and fruits. And as I said, the evidence is stronger for heart disease than it is for cancer.

Judy:

So do you still have that five a day program that you were pushing a few years ago?

Dr. Thun:

Well that was the, first of all that's the National Cancer Institute's program.

Judy:

Oh, I am sorry.

Dr. Thun:

But they had increased it really. Five a day was based on trying to double what the average American was eating, and what the average American was eating included french fries as a vegetable. So actually the recommendation now is higher. I think that the American Cancer Society recommendation is to eat and a healthy diet with an emphasis on plant foods. And the point is that you have to eat something and therefore you want to have a diet in which most of what you're eating comes from plants and less of what you're eating comes from meats and dairy and saturated fats, etc.

Judy:

Well it's interesting, I didn't realize that the evidence for the fruits and veggies had gotten weaker. And the same is kind of true for vitamin supplements, isn't that right? I mean that a lot of vitamin supplements have kind of been de-bunked as cancer preventors. Is that right?

Dr. Thun:

Yes, I would say that. I would put fruits and vegetables in a different category than vitamins because the fruits and vegetables are still recommended by all major health organizations for the reasons I mentioned. Now supplements is another category because there has been evidence in randomized trials in which there's been counter effects for people in substances like beta-carotene and smoking. And the supplement industry is not required to meet the same evidence of efficacy that the FDA requires for drugs.

Judy:

Right.

Dr. Thun:

So there still is potential that for some supplements to reduce cancer risks, particularly calcium in women. And there's the big trial on selenium and vitamin E going on for prostate cancer, but it has been extremely difficult to prove that supplements are beneficial in reducing cancer risks except in areas where there is a severe nutrient deficiency like remote areas of China.

Judy:

Okay. So we are left with sort of the basic "eat right and exercise and drink in moderation and don't smoke" advice, the stuff we have been told for years and years. Over all, how are we faring with cancer? What are the big trends? Are we doing better? Are fewer people getting cancer these days? Are fewer people dying from it? What's the big picture here?

Dr. Thun:

Well, the big picture is promising although we have a long way to go. And the progress has been greater in reducing death rates from cancer than reducing incidence, although incidence rates are also falling for an essential number of cancers. But between 1991 and 2004, the death rates from all cancers combined decreased by about 1 percent a year. So it's a total of over 13 percent.

Judy:

And that's because of better treatments or that's lower incidence? Or both?

Dr. Thun:

It's both. In the case of the tobacco-related cancers particularly the decrease in lung cancer death rates in men, the real reason has been the reduction from smoking over the past 30-40 years. In the case of prostate cancer in which there has been a 35 percent decrease from 1991 to 2004 in the death rate, it's not entirely clear, but it is likely that both early detection and treatment contribute to that.

In the case of breast cancer, death rates been little over 25 percent decrease from 1991 to 2004 and that is a function of early detection and treatment. And for colon cancer, put men and woman together and it is about a 25 percent decrease. So that's the good news for death rates. Two ways in which enormous progress still needs to be made is that there is still a need to be able to screen patients so that only those who are going to profit from a treatment get treated.

Judy:

I am sorry to interrupt. We are just about out of time. But we have time for a final thought. So Dr. Michael Thun the epidemiologist from the American Cancer Society, what parting thought would you like to leave us with?

Dr. Thun:

I'd like to leave with a parting thought that there really are no shortcuts, and whatever other things one may be concerned about with cancer, keep the main things at the top of the list.

Judy:

That's great.

Dr. Thun:

And do everything you can to work on them.

Judy:

Thank you very much, Dr. Thun. And I'd like to thank you, the listeners, for joining us. Until next week, I'm Judy Foreman. Good night.